Evolution of Electronic Properties of Graphene Nanoribbons with Progressive Carving into 1D Porous and Meandering Structures

Graphene nanoribbons (GNRs) exhibit highly tunable electronic, magnetic, and optical properties that depend on ribbon's width, edge geometry, and topology. We report the on-surface synthesis and characterization of a straight N = 15 armchair GNR incorporating periodic [18]annulene nanopores (15-pGNR). This ribbon serves as an intermediate structure between the pristine N = 15 armchair GNR (15-AGNR) and the chevron GNR (cGNR), enabling systematic investigation of how electronic structure evolves upon progressive modification of the 15-AGNR backbone. The 15-pGNR was synthesized on single-crystal Au substrates under ultra-high-vacuum conditions using a custom molecular precursor. Its atomic structure and electronic properties were characterized by STM, nc-AFM, STS, and ARPES. Comparative experimental and theoretical analysis reveals that incorporation of periodic nanopores more than doubles the band gap relative to 15-AGNR, while the band gaps of 15-pGNR and cGNR differ by only ~15%. The observed band gap widening originates from the combined effects of graphene perforation and lateral quantum confinement.